A plane curve also called the Cross Curve and Policeman on Point Duty Curve (Cundy and Rollett 1989).
It is given by the equation

(1) |

(2) |

(3) |

(4) |

(5) | |||

(6) |

The Curvature is

(7) |

**References**

Cundy, H. and Rollett, A. *Mathematical Models, 3rd ed.* Stradbroke, England: Tarquin Pub., p. 71, 1989.

Lawrence, J. D. *A Catalog of Special Plane Curves.* New York: Dover, pp. 127 and 130-131, 1972.

© 1996-9

1999-05-25